ES10 特性的完整指南小结

const b = 1n; // 追加 n 以创建 BigInt

const limit = Number.MAX_SAFE_INTEGER;
⇨ 9007199254740991
limit + 1;
⇨ 9007199254740992
limit + 2;
⇨ 9007199254740992 <--- MAX_SAFE_INTEGER + 1 exceeded
const larger = 9007199254740991n;
⇨ 9007199254740991n
const integer = BigInt(9007199254740991); // initialize with number
⇨ 9007199254740991n
const same = BigInt("9007199254740991"); // initialize with "string"
⇨ 9007199254740991n

typeof 10;
⇨ 'number'
typeof 10n;
⇨ 'bigint'

10n === BigInt(10);
⇨ true
10n == 10;
⇨ true

200n / 10n
⇨ 20n
200n / 20
⇨ Uncaught TypeError:
 Cannot mix BigInt and other types, use explicit conversions <

-100n
⇨ -100n
+100n
⇨ Uncaught TypeError:
 Cannot convert a BigInt value to a number

let string = 'Hello';
let matches = string.match('l');
console.log(matches[0]); // "l"

let string = "Hello";
let matches = string.match(/l/);
console.log(matches[0]); // "l"

let string = "Hello";
let ret = string.match(/l/g); // (2) [“l”, “l”];

const string = 'black*raven lime*parrot white*seagull';
const regex = /(?<color>.*?)\*(?<bird>[a-z0-9]+)/g;
while (match = regex.exec(string))
{
 let value = match[0];
 let index = match.index;
 let input = match.input;
 console.log(`${value} at ${index} with '${input}'`);
console.log(match.groups.color);
 console.log(match.groups.bird);
}

// Match all occurrences of the letters: "e" or "l" 
let iterator = "hello".matchAll(/[el]/);
for (const match of iterator)
 console.log(match);

const string = 'black*raven lime*parrot white*seagull';
const regex = /(?<color>.*?)\*(?<bird>[a-z0-9]+)/;
for (const match of string.matchAll(regex)) {
 let value = match[0];
 let index = match.index;
 let input = match.input;
 console.log(`${value} at ${index} with '${input}'`);
console.log(match.groups.color);
 console.log(match.groups.bird);
}

element.addEventListener('click', async() => {
 const module = await import(`./api-scripts/button-click.js`);
 module.clickEvent();
})

let multi = [1,2,3,[4,5,6,[7,8,9,[10,11,12]]]];
multi.flat();    // [1,2,3,4,5,6,Array(4)]
multi.flat().flat();  // [1,2,3,4,5,6,7,8,9,Array(3)]
multi.flat().flat().flat(); // [1,2,3,4,5,6,7,8,9,10,11,12]
multi.flat(Infinity);  // [1,2,3,4,5,6,7,8,9,10,11,12]

let array = [1, 2, 3, 4, 5];
array.map(x => [x, x * 2]);


let array = [1, 2, 3, 4, 5];
array.map(x => [x, x * 2]);

array.flatMap(v => [v, v * 2]);
[1, 2, 2, 4, 3, 6, 4, 8, 5, 10]

let obj = { apple : 10, orange : 20, banana : 30 };
let entries = Object.entries(obj);
entries;
(3) [Array(2), Array(2), Array(2)]
 0: (2) ["apple", 10]
 1: (2) ["orange", 20]
 2: (2) ["banana", 30]
let fromEntries = Object.fromEntries(entries);
{ apple: 10, orange: 20, banana: 30 }

let greeting = "  Space around  ";
greeting.trimEnd(); // "  Space around";
greeting.trimStart(); // "Space around  ";

'{ “prop1” : 1, "prop2" : 2 }'; // A well-formed JSON format string

'{ “prop1” : 1, "meth" : () => {}}'; // Not JSON format string

let object_literal = { property: 1, meth: () => {} };

var fruit = [
 { name: "Apple",  count: 13, },
 { name: "Pear",  count: 12, },
 { name: "Banana",  count: 12, },
 { name: "Strawberry", count: 11, },
 { name: "Cherry",  count: 11, },
 { name: "Blackberry", count: 10, },
 { name: "Pineapple", count: 10, }
];
// 创建排序函数:
let my_sort = (a, b) => a.count - b.count;
// 执行稳定的ES10排序:
let sorted = fruit.sort(my_sort);
console.log(sorted);

function () { console.log('Hello there.'); }.toString();

⇨ function () { console.log('Hello there.'); }

Number.parseInt.toString();
⇨ function parseInt() { [native code] }

function () { }.bind(0).toString();
⇨ function () { [native code] }

Symbol.toString();
⇨ function Symbol() { [native code] }

function* () { }.toString();
⇨ function* () { }

Function.prototype.toString.call({});
⇨ Function.prototype.toString requires that 'this' be a Function"

try {
 // Call a non-existing function undefined_Function
 undefined_Function("I'm trying");
}
catch(error) {
 // Display the error if statements inside try above fail
 console.log( error ); // undefined_Function is undefined
}

try {
 JSON.parse(text); // <--- this will fail with "text not defined"
 return true; <--- exit without error even if there is one
}
catch (redundant_sometmes) <--- this makes error variable redundant
{
 return false;
}

(() => {
 try {
  JSON.parse(text)
  return true
 } catch(err) {
  return false
 }
})()
=> false

try {
 JSON.parse(text);
 return true;
}
catch
{
 return false;
}

var getGlobal = function () {
 if (typeof self !== 'undefined') { return self; }
 if (typeof window !== 'undefined') { return window; }
 if (typeof global !== 'undefined') { return global; }
 throw new Error('unable to locate global object');
};

// 访问全局数组构造函数
globalThis.Array(0, 1, 2);
⇨ [0, 1, 2]

// 类似于 ES5 之前的 window.v = { flag: true }
globalThis.v = { flag: true };

console.log(globalThis.v);
⇨ { flag: true }

let mySymbol = 'My Symbol';
let symObj = Symbol(mySymbol);
symObj; // Symbol(My Symbol)
symObj.description; // "My Symbol"

$ ./index.js

$ node index.js

class Raven extends Bird {
#state = { eggs: 10};
// getter
 get #eggs() { 
  return state.eggs;
 }
// setter
 set #eggs(value) {
  this.#state.eggs = value;
 }
#lay() {
  this.#eggs++;
 }
constructor() {
  super();
  this.#lay.bind(this);
 }
#render() {
  /* paint UI */
 }
}